The present invention disclosed herein relates to a nonvolatile memory, and more particularly, to a nonvolatile memory and a driving method thereof, which enable a multi program operation.
Generally, flash memory may be categorized into NAND flash memory and NOR flash memory. NOR flash memory has a structure in which each memory cell is connected to a bit line and a word line. Accordingly, NOR flash memory has the characteristic of superior random access speed.
NAND flash memory includes a plurality of memory cells that are connected in series, and thus it requires only one contact per cell string. Accordingly, NAND flash memory is characterized by a superior degree of integration.
Recently, research has been made on multi bit cells that may store a plurality of data in one memory cell for further improving the degree of integration of flash memory. A memory cell using such a scheme is commonly called a Multi-Level Cell (MLC). In contrast, single-bit memory cells are called Single-Level Cells (SLC). Generally, an MLC has two or more threshold voltage distributions.